The Pelican BriefIn suburban Georgetown a killer's Reeboks whisper on the front floor of a posh home In a seedy D. C. porno house a patron is swiftly garroted to death The next day America learns that two of its Supreme Court justices have been assassinated. And in New Orleans, a young law student prepares a legal brief To Darby Shaw it was no more than a legal shot in the dark, a brilliant guess. To the Washington establishment it was political dynamite. Suddenly